Trimmer condenser



Aug. i, 1956 HALL ETAL 2,516,,981

TRIMMER CONDENSER Filed Feb. 19, 1948 FIG. 1. FIG 2 24-5 r l i Z! I I g; .1

I2 l2 4 IO 3 3e zt INVENTORS Emery L Hall BY LOUlS W Schremer Affy iatented Aug. 1, 1950 Emery n nau, Chicago, and Louis w. Schreiner Des Plaincs, Ill., assignors to Belmont Radio Corporation, Chicago, 111., a

nois

corporation of Illi- Application February 19, 1948, Serial No. 9,364

This invention relates to capacitors, and particularly to trimmers and other smalL adjustable capacitors.

Large quantities of trimmers are used in electronic equipmentsuch as radio and television sets to afford accurateand minute frequency adjustments. Reliable trimmers whichcan be pro- 'duced at low cost are very much in demand. In

the higher-frequency circuits particularly it has been diflicult to produce acceptable, inexpensive trimmers because of the extremely fine adjustments which are required.

An object of the present invention is to provide a novel low-cost trimmer which gives satisfactory and dependable service, especially at the higher frequencies. I

Another objectis to. provide an improved adjustable capacitor of'the tubular type having a minimum of parts.

A still further object is to provide an improved trimmer of exceptionally small size having a wide range of adjustment. I

A feature which characterizes my invention is the provision of a screw asthe inner plate or electrode of the capacitor. This screw is threaded into a stationary dielectric sleeveon which is disposed a metallic sleeve that serves as the outer plate or electrode of the capacitor. By turning the screw, the capacitance of the trimmer may be varied.

The foregoing and other objects, features and disassembled relation.

In practicing the invention, a split tube of dielectric material is fitted within a metallic sleeve which forms one plate or conductor of the capacitor. The metallic sleeve has a lengthwise split therein to provide a spring action. The dielectric pieces are composed of molded or extruded insulating material. One endoi' the dielectric tube is adapted to fit a standard coil mounting. A metallic screw is threaded into the dielectric to form the second of the capacitor. v

Referring now to the drawing, the dielectric plate or conductor 4 Claims ((31. -415) portion of the capacitor comprises a tubular sleeveor bushing III which is longitudinally divided into two complementary half-sections l2 and H. These dielectric pieces are made of molded or extruded polystyrene or other suitable insulating material. and they are of identical configuration so that the same die can,be used in forming them. The dielectric bushing I0 is providedwith internal threads I6 which preferably are molded in the pieces l2 and It. By

using well known double thread construction the threads of the sections l2 and M will mate properly when the sections are of identical construction. The base of each piece I2 and I4 is enlarged as indicated at l8. This base portion I8 is received in acup-shaped, metallic holder 20 which may consist of a standard member. Sharp points 2| on the holder 20 bear against the base 18 to keep it from turning or being pulled out inadvertently.

The outer plate or'conductive electrode of the capacitor consists of a metallic sleeve 22 which is longitudinally slit as indicated at 24. The sleeve 22 is fitted over the bushing l0 and resiliently holds the two'sections l2 and I4 of the bushing I ll together. In Fig. 2 the bushing I0 is shown partially inserted in the sleeve 22, and in Fig. 1 it is shown fully inserted in this sleeve. A soldering lug 26 is provided on the sleeve 22 for making electrical connection to an external condoctor. The inner plate or electrode of the capacitor comprises a metallic screw 28, the shank of which is received in the threaded interior of the bushing Ill. The screw 28 is provided with the usual slotted head 30 so that the longitudinal position of the screw in the bushing I0 may be adjusted by turning the screw.

The complete capacitor unit thus comprises the metallic sleeve 22, the dielectric sleeve or bushing Hi, the holder 20 and the screw 28. The holder 20 has locking lugs 32 which resiliently bear against the shank of the screw 28 to prevent loosening of the screw 28. The dielectric tube I0 is tightly engaged with both the screw 28 and the outer sleeve 22, and if desired, a suitable moisture-resistant sealing substance may be employed between these parts. The unit is adapted to be mounted on a chassis 34 or like supporting member, the holder 20 being inserted into a suitable aperture therein. Arms or tabs 36 on the holder 20 bear against one side of the chassis 34, and the other side of the chassis is gripped by lugs or wings 38. A lug 40 depending from one of the tabs 36 is adapted to drop into a recessed portion or the aperture in the chassis in which coil mounting the holder 20 is mounted, as to prevent the unit tremely small and compact with a minimum number of parts. The spring tension of the outer sleeve 22 causes uniform contact between the dielectric and the screw which gives essentially linear capacity variation with screw rotation. Also, by having the dielectric threaded, the capacity of the unit is increased. Linearity of capacity change could be obtained only by using very accurate dimensions if the dielectric were a smooth tube with an air space between the screw and the dielectric as movement of the screw would cause changes in the air space. While we have found it to be particularly useful in television circuits, it is not necessarily limited to such use as it may be adapted for other purposes within the scope of the present teachings.

Thus, while we have illustrated anddescribed a particular embodiment of the invention, such embodiment is capable of modification without departing from the spirit of the invention, and it is intended to, cover all suchmodifications by the appended claims.

We claim: I v

' 1. An adjustable capacitor of the tubular type including in combination a conductive threaded screw, a dielectric tube having internal threads for receiving said screw, said dielectric tube ing 4 3. A concentric trimmer capacitor including in combination a dielectric bushing having two substantially identical molded semi-cylindrical sections, said sections having threaded portions forming aninner opening with a continuing double thread therethroughwhen said sections are positioned in complementary relation, an inner electrode having threads thereon corresponding to the threads of said bushing and being positioned between'said sections of said bushing, and a resilient sleeve-like outer electrode surrounding said bushing and resiliently holding the sections thereof together with said inner electrode therebetween. I

4. A concentric trimmer capacitor including in combination a tubular dielectric bushing having an enlarged portion at one end thereof, said bush eluding a plurality of molded longitudinal sec- 2. An adjustable capacitor of the tubular type including in combination a dielectric bushing having two substantially identical semi-cylindrical sections arranged in complementary relation, a conducting screw positioned between said sections, and a longitudinally slit resilient metallic sleeve positioned about said bushing and holding the sections thereof firmly against said screw, said screw and said sleeve constituting the 5 conductive electrodes of the capacitor, with the capacity thereof being determined by the relative positions of said'screw and said sleeve.

ing being formed of two substantially identical molded semi-cylindrical sections, said sections having threaded portions forming an inner opening with a continuing double thread. therethrough' when said sections. are positioned in complementary relation, an inner electrode having threads thereoncorresponding to the threads of said bushing and being positioned between said sections of said bushing, arid a longitudinally split resilient sleeve-like outer electrode surrounding said bushing and resiliently holding the sections thereof together with said inner electrode therebetween, said enlarged portion of said tubular bushing forming a mounting 'for the capacitor.

EMERY L. HALL.

LOUIS W; SCHREINER.

REFERENCES CITED The following references are of record in-th file of this patent: I

UNITED, STATES PATENTS France July 23, 1928 

